An optical reception device receives signal light or Amplified Spontaneous Emission (ASE) light as input light supplied from a Wavelength Division Multiplexing (WDM) device. ASE light is light in which no data is identified and reproduced as a result of an identification and reproduction process performed by the optical reception device. ASE light is light noise generated when a WDM device amplifies light. Signal light is light in which data is identified and reproduced as a result of an identification and reproduction process performed by the optical reception device. When signal light is input, ASE light may be input together with the signal light
Upon receiving input light, a conventional optical reception device identifies and reproduces data from the input light and, if data is identified and reproduced from the input light, determines that the input light contains signal light. In other words, the optical reception device subjects input light to the operation for the identification and reproduction of data and determines the presence or absence of signal light in the input light on the principle that data cannot be identified and reproduced if the input light consists only of ASE light. Japanese Patent Application Laid-Open No. 2008-098975 discloses a method in which signal light whose waveform has been deteriorated by wavelength dispersion is subjected to dispersion compensation.
The foregoing conventional technology suffers from the problem that a determination cannot be accurately made whether input light contains signal, light. That is, in order to determine whether input light contains signal light, in the conventional technology the optical reception device has to subject input light to a process of identification and reproduction of data.